The present invention is related to alternators, and more specifically to alternators which are intended for operation in agricultural or industrial construction environments.
For alternators used in agricultural or industrial construction environments, in addition to typically requiring a high alternator output, the alternator must be constructed to withstand the potential hostile ambient atmosphere which may surround the alternator. This hostile ambient atmosphere will typically include dust contaminating particles, and, in the case of agricultural environments, other particle debris such as wheat or corn chaff, for example.
Because of the hostile environments in which these alternators must operate, the alternator construction conventionally used in automobile vehicles has been found not to be suitable. This is because in conventional alternator construction, a fan assembly is used to provide cooling of the alternator rectifying diodes and stator and rotor assemblies by implementing air flow through the entire alternator which has an outer protective housing. Thus the typical alternator housing will comprise effectively open rear and front housing portions joined together with a fan assembly mounted on an end of the alternator drive shaft to insure air flow past all alternator components positioned within the housing. When such an alternator is subject to particle contamination in the ambient atmosphere surrounding the housing, this results in pulling the contaminents, for example dust particles, into the alternator housing and having the contaminents build up on components within the alternator and effectively choke off the air circulation which was required. This air circulation is needed for the alternator to provide its rated output without overheating. Also particle contamination can adversely affect the alternator drive shaft bearings if they are not sufficiently protected. The end result is that the alternator, if not protected by frequent cleaning, would overheat due to insufficient air cooling and incur a catastrophic failure of either the rotor, stator, rectifying diode or voltage regulator subassemblies, or other components. Thus, continuous high power output operation of such alternators for relatively long durations was not possible.
In order to provide an alternator which could continuously operate under the extreme environment which may exist in agricultural or industrial construction usage, several prior modifications of the conventional alternator structure have been proposed. However, all of these modifications have proved unacceptable for one reason or another. One of these previous methods comprises providing particle or debris screens to prevent debris from entering the alternator housing and covering the stator and rotor windings, and rectifying diodes, wherein if these elements are covered by particles, air cooling is prevented and a failure may occur. The problem with the use of such debris screens is that these screens will frequently clog due to the debris which they are screening out, and only by frequently cleaning these screens can heat related failures be prevented. Thus this solution is totally unacceptable since its only advantage is making it somewhat easier to periodically clean the alternator, by cleaning just the screen, when it is operated in an hostile environment, rather than allowing the alternator to properly continuously operate for long durations in a hostile environment.
Another proposed solution is to totally enclose all of the alternator critical parts within a substantially air closed alternator housing. However, when such a solution is implemented, it has been found that with no air cooling the power output of these alternators must be regulated to a relatively low magnitude, or heat related failures will occur due to overheating of the alternator components. In addition, these designs incur the additional expense of a substantial number of gaskets which are required to keep all dust and other particle contaminents away from the alternator critical elements. Thus continuous operation was provided, but only at a reduced output level.
Since clearly cooling of the alternator structure was desired, another design has been proposed which involves totally enclosing all of the alternator critical components within an outer housing, and then providing oil cooling for the housing and alternator components. This solution is extremely expensive since it requires a substantial amount of oil conduit tubing and pressurized gasketing for the tubing, and it requires implementing a pressure driven oil flow. Thus an extremely expensive alternator is the end result of this oil cooled totally enclosed design, but at least an alternator with a high output and capable of continuously operating for long durations in an extremely hostile environment was provided.